1. Field of the Invention
The present invention relates to a calibration apparatus of an on-vehicle camera (hereinafter referred to as “on-vehicle camera calibration apparatus” as needed) comprising an image processing device.
2. Description of the Related Art
In an on-vehicle camera comprising an image processing device, a role of the camera increasingly becomes important for the purpose of safe running of a vehicle, an advanced position calibration of a car navigation, and the like; and an image processing technology for enhancing an accuracy for recognizing an object on a road surface or on a road are variously proposed. However, in many cases an installation height and imaging angle of an on-vehicle camera attached to a vehicle change from an initial set condition over time due to such an up-down vibration, gravitation by a sudden acceleration and deceleration, and other impacts. In these cases, because accurate image processing information cannot be obtained, it becomes necessary to periodically calibrate an optical axis of the camera.
Therefore, there are introduced a method of using a reference marker, of which a relative position relationship to a vehicle is known, and calibrating an on-vehicle camera (for example, see claim 1 in Japanese Patent Laid-Open Publication No. 2004-200819); and a method of calculating an attitude parameter of an on-vehicle camera from a road vanishing point (for example, see claim 1 in Japanese Patent Laid-Open Publication No. H07-77431).
In the JP 2004-200819 it is necessary to prepare the reference marker for calibrating an optical axis calibration of the camera, and the calibration is not performed unless the vehicle is in a stop state. In the JP H07-77431 there are many restrictions in order that the road vanishing point becomes calculable (for example, paragraph 0054), and because the point is also easily influenced under a view condition due to weather, an opportunity when a favorable calibration can be performed is restricted.
Consequently, there is a need for an on-vehicle camera calibration apparatus that enables an optical axis calibration of the camera from information obtained at a higher frequency on a road even if the vehicle is running.